Dear JOAN: Any explanation of that incredibly vivid rainbow last week? Never seen anything like it -- at sunset with no rain here. Hope to learn more.

Kristen B.

Cyberspace

Dear Kristen: Sadly, I missed it, but I've heard it was spectacular.

There are a lot of things in play when it comes to determining whether there is a rainbow, where it appears, how bright it is, whether it's a double or even tripled one. But apparently conditions were near perfect the other day.

Basically, a rainbow is created when light from the sun -- or even the moon -- enters a droplet of water. Raindrops are slightly elongated spheres and when light enters one, it is refracted, splitting the white light into its various parts.

The rays are reflected inside the raindrop and emerge toward the direction the light came. And because each color wave exits at a slightly different angle, that's why you see the layers or bands of color.

For a rainbow to occur, its needs three things -- a light source, water and someone to see it. The water, usually rain, doesn't have to be falling on your head for there to be a rainbow. You just need to be standing with the sun at your back and water droplets somewhere in front. In this case, there was some moisture falling on Mount Diablo as the sun was dropping in the west.

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The best rainbows are produced in the late afternoon, when the sun's angle hits the water droplets at the perfect spot. And the bigger the droplets, the brighter the rainbow.

Dear Joan: I have a hummingbird feeder and would like to know how to mix the sugar water solution with red food coloring.

Leonard M.

San Jose

Dear Leonard: For a long time, companies have been selling humming bird solution that is red, the theory being that hummingbirds are attracted to red flowers, thus red food.

However, some believe the red coloring may make the birds ill or stain the tail feathers, leading to a confused mating season. Although there have been no definitive studies on the subject, you don't need to color the nectar to attract the birds, so let's be safe and not add it.

The hummers can find the nectar no matter what color it is or what color the feeder is. Still, if you think red will draw them in, get a feeder that has red in it and leave the nectar clear.

The formula for hummingbird nectar is four-to-one -- four parts water to one part sugar. Heating the solution for a couple of minutes will help dissolve the sugar and slow fermentation. If your water is high in minerals, you might to use a purifier.

Good stuff

Looking for a good dog? You can now adopt dogs from noon to 3 p.m. every Sunday, starting Sept. 16, at Animal Services, 4800 Imhoff Place, Martinez. Add some love to your home -- the life you save may be your own.

Tony LaRussa's Animal Rescue Foundation is hosting its ninth annual Wine and Whiskers fundraiser, 5 to 8 p.m. Sept. 22, 2890 Mitchell Drive, Walnut Creek. The evening of food and wine tasting also features live music and an auction. All proceeds benefit ARF's lifesaving programs. Tickets are $80; go to www.arf.net or call Kathleen Huls at 925-296-3118 for reservations.